Class TCastleApplication

Unit

Declaration

type TCastleApplication = class(TCustomApplication)

Description

Application, managing all open TCastleWindow (OpenGL windows). This tracks all open instances of TCastleWindow and implements message loop. It also handles some global tasks like managing the screen (changing current screen resolution and/or bit depth etc.)

The only instance of this class should be in Application variable. Don't create any other instances of class TCastleApplication, there's no point in doing that.

Hierarchy

Overview

Fields

Public VideoResize: boolean;
Public VideoResizeWidth: integer;
Public VideoResizeheight: integer;

Methods

Protected procedure DoLog(EventType: TEventType; const Msg: String); override;
Protected procedure DoRun; override;
Public procedure Notification(AComponent: TComponent; Operation: TOperation); override;
Public function VideoSettingsDescribe: string;
Public function TryVideoChange: boolean;
Public procedure VideoChange(OnErrorWarnUserAndContinue: boolean);
Public procedure VideoReset;
Public function ScreenHeight: integer;
Public function ScreenWidth: integer;
Public function ScreenStatusBarScaledHeight: Cardinal;
Public function OpenWindowsCount: integer;
Public function ProcessMessage(WaitForMessage, WaitToLimitFPS: boolean): boolean;
Public function ProcessAllMessages: boolean;
Public procedure Quit; deprecated 'Use Terminate';
Public procedure Terminate; override;
Public procedure Run;
Public function BackendName: string;
Public constructor Create(AOwner: TComponent); override;
Public destructor Destroy; override;
Public procedure HandleException(Sender: TObject); override;
Public procedure ParseStandardParameters;
Public function OpenGLES: Boolean;

Properties

Public property XDisplayName: string read FXDisplayName write FXDisplayName;
Public property VideoColorBits: integer read FVideoColorBits write FVideoColorBits default 0;
Public property VideoFrequency: Cardinal read FVideoFrequency write FVideoFrequency default 0;
Public property OpenWindows[Index:integer]: TCastleWindow read GetOpenWindows;
Public property OnInitialize: TProcedure read FOnInitialize write FOnInitialize;
Public property OnInitializeEvent: TNotifyEvent read FOnInitializeEvent write FOnInitializeEvent;
Public property OnUpdate: TUpdateFunc read FOnUpdate write FOnUpdate;
Public property OnIdle: TUpdateFunc read FOnUpdate write FOnUpdate; deprecated;
Public property OnTimer: TProcedure read FOnTimer write FOnTimer; deprecated 'use TCastleTimer to perform periodic operations, or track time delay in OnUpdate';
Public property TimerMilisec: Cardinal read FTimerMilisec write FTimerMilisec default 1000; deprecated 'use TCastleTimer to perform periodic operations, or track time delay in OnUpdate';
Public property MainWindow: TCastleWindow read FMainWindow write SetMainWindow;
Public property UserAgent: string read FUserAgent;
Public property LimitFPS: Single read GetLimitFPS write SetLimitFPS; deprecated 'use ApplicationProperties.LimitFps';
Public property Version: string read GetVersion write SetVersion; deprecated 'use ApplicationProperties.Version';
Public property TouchDevice: boolean read GetTouchDevice write SetTouchDevice; deprecated 'use ApplicationProperties.TouchDevice';

Description

Fields

Public VideoResize: boolean;

If VideoResize, then next VideoChange call will try to resize the screen to given VideoResizeWidth / VideoResizeHeight. Otherwise, next TryVideoChange and VideoChange will use default screen size.

Public VideoResizeWidth: integer;
 
Public VideoResizeheight: integer;
 

Methods

Protected procedure DoLog(EventType: TEventType; const Msg: String); override;

Override TCustomApplication to pass TCustomApplication.Log to CastleLog logger.

Protected procedure DoRun; override;

Every backend must override this. TCustomApplication will automatically catch exceptions occuring inside DoRun.

Public procedure Notification(AComponent: TComponent; Operation: TOperation); override;
 
Public function VideoSettingsDescribe: string;

Describe the changes recorded in variables VideoXxx, used by VideoChange and TryVideoChange. This is a multiline string, each line is indented by 2 spaces, always ends with CastleUtils.NL.

Public function TryVideoChange: boolean;

Change the screen size, color bits and such, following the directions you set in VideoColorBits, VideoResize, VideoResizeWidth / VideoResizeHeight, and VideoFrequency variables. Returns True if success.

TODO: Expose methods like EnumeratePossibleVideoConfigurations to predict what video settings are possible.

TODO: Prefix "Video" for the family of these functions is not clear. Something like "Screen" would be better.

Public procedure VideoChange(OnErrorWarnUserAndContinue: boolean);

Change the screen size, color bits and such, following the directions you set in VideoColorBits, VideoResize, VideoResizeWidth / VideoResizeHeight, and VideoFrequency variables. This actually just calls TryVideoChange and checks the result.

If not success: if OnErrorWarnUserAndContinue then we'll display a warning and continue. If not OnErrorWarnUserAndContinue then we'll raise an Exception.

Exceptions raised
Exception
If video mode change failed, and OnErrorWarnUserAndContinue = false.
Public procedure VideoReset;

Return default screen video mode. If you never called TryVideoChange (with success), then this does nothing. This is automatically called in Application.Destroy, so at finalization of this unit. This way your game nicely restores screen resolution for user.

Public function ScreenHeight: integer;
 
Public function ScreenWidth: integer;
 
Public function ScreenStatusBarScaledHeight: Cardinal;
 
Public function OpenWindowsCount: integer;

List of all open windows.

Public function ProcessMessage(WaitForMessage, WaitToLimitFPS: boolean): boolean;

Process messages from the window system. You have to call this repeatedly to process key presses, mouse events, redraws and everything else. Messages are processed and appropriate window callbacks are called, like TCastleWindow.OnRender, TCastleWindow.OnUpdate, TCastleWindow.OnKeyPress and many others.

For simple programs calling the Run method is usually the best solution, Run just calls ProcessMessage in a loop. Manually using the ProcessMessage method allows you to implement modal dialog boxes (generally any kind of "display something until something happens" behavior). Make your own event loop like this:

while not SomethingHappened do
  Application.ProcessMessages(...);

This can used to implement routines that wait until a modal dialog box returns, like MessageOK or MessageYesNo.

For comfort, returns not Terminated. So it returns True if we should continue, that is if Terminate method was not called (directly or by closing the last window). If you want to check it (if you allow the user at all to close the application during modal box or such) you can do:

while not SomethingHappened do
  if not Application.ProcessMessage(...) then
    Break;

Do not assume too much about message processing internals. For example, not all ProcessMessage calls cause redraw, even if redraw is requested by Invalidate. When we have messages to process, we generally don't call redraw or even OnUpdate.

Parameters
WaitForMessage
If True (and some other conditions are met, for example we do not have to call OnUpdate continuosly) then we can block, waiting for an event to process.

Set this to True whenever you can, that is whenever your program only responds to user inputs (as opposed to making some operations, like animation or loading or ray-tracing something). Generally, when SomethingHappened from the example pseudo-code above can only be changed by user events (e.g. user has to click something; nothing happens if user doesn't click for 5 minutes or 5 hours). This allows to let OS and CPU have some rest, and spend time on other applications, or just sleep and conserve laptop battery power.

WaitToLimitFPS
If True, then we have backup mechanism for limiting CPU usage. When WaitForMessage mechanism cannot be used (becasue WaitForMessage is False or some other conditions disallow it), and user doesn't throw events at us (we don't want to sleep when user produces many events e.g. by mouse move), then we can do a small sleep to stabilize number of ProcessMessage calls at LimitFPS per second.

Set this to True whenever you can, that is whenever you don't need ProcessMessage to return as fast as it can. For example, when you're displaying some animation, then displaying LimitFPS frames should be enough. OTOH, if you really do something that should be done as fast as possible (like loading some file or ray-tracing) you probably have to set this to False.

Public function ProcessAllMessages: boolean;

Processes all pending messages. Do not wait for anything.

Contrast this with ProcessMessage method, that processes only a single event. Or no event at all (when no events were pending and AllowSuspend = False). This means that after calling ProcessMessage once, you may have many messages left in the queue (especially mouse move together with key presses typically makes a lot of events). So it's not good to use if you want to react timely to some user requests, e.g. when you do something time-consuming and allow user to break the task with Escape key.

ProcessAllMessages is like calling in a loop ProcessMessage(false, false), ends when ProcessMessage(false, false) didn't process any message or when quit was called (or last window closed).

So ProcessAllMessages makes sure we have processed all pending events, thus we are up-to-date with window system requests.

Public procedure Quit; deprecated 'Use Terminate';

Warning: this symbol is deprecated: Use Terminate

 
Public procedure Terminate; override;
 
Public procedure Run;

Run the program using TCastleWindow, by doing the event loop. Think of it as just a shortcut for "while ProcessMessage do ;".

Note that this does nothing if OpenWindowsCount = 0, that is there are no open windows. Besides the obvious reason (you didn't call TCastleWindow.Open on any window...) this may also happen if you called Close (or Application.Quit) from your window OnOpen / OnResize callback. In such case no event would probably reach our program, and user would have no chance to quit, so Run just refuses to work and exits immediately without any error.

Public function BackendName: string;
 
Public constructor Create(AOwner: TComponent); override;
 
Public destructor Destroy; override;
 
Public procedure HandleException(Sender: TObject); override;
 
Public procedure ParseStandardParameters;

Handle standard command-line parameters of Castle Game Engine programs. Handles:

Public function OpenGLES: Boolean;

Are we using OpenGLES for rendering.

Properties

Public property XDisplayName: string read FXDisplayName write FXDisplayName;

Set XDisplay name, this will be used for all TCastleWindow that will be subsequently initialized by TCastleWindow.Open.

Note that this is exposed by GTK even for non-XWindows platforms, but I don't know what it does there.

Public property VideoColorBits: integer read FVideoColorBits write FVideoColorBits default 0;

Color bits per pixel that will be set by next VideoChange call, and that are tried to be used at TCastleWindow.Open. Zero means that system default is used.

Public property VideoFrequency: Cardinal read FVideoFrequency write FVideoFrequency default 0;

Video frequency to set in next VideoChange call. Leave as 0 to use system default.

Public property OpenWindows[Index:integer]: TCastleWindow read GetOpenWindows;
 
Public property OnInitialize: TProcedure read FOnInitialize write FOnInitialize;

The application and CastleWindow backend is initialized. Called only once, at the very beginning of the game, when we're ready to load everything and the first OpenGL context is initialized (right before calling TCastleWindow.OnOpen).

For targets like Android or iOS, you should not do anything (even reading files) before this callback occurs. Only when this occurs, we know that external process told us "Ok, you're ready". So you should put all the game initialization in an Application.OnInitialize callback. It will be automatically called by CastleWindow backend when we're really ready (actually, a little later — when OpenGL context is active, to allow you to display progress bars etc. when loading).

Public property OnInitializeEvent: TNotifyEvent read FOnInitializeEvent write FOnInitializeEvent;
 
Public property OnUpdate: TUpdateFunc read FOnUpdate write FOnUpdate;

Continuously occuring event.

See also
TCastleWindow.OnUpdate
Continuously occuring event, called for all open windows.
Public property OnIdle: TUpdateFunc read FOnUpdate write FOnUpdate; deprecated;

Warning: this symbol is deprecated.

Deprecated name for OnUpdate.

Public property OnTimer: TProcedure read FOnTimer write FOnTimer; deprecated 'use TCastleTimer to perform periodic operations, or track time delay in OnUpdate';

Warning: this symbol is deprecated: use TCastleTimer to perform periodic operations, or track time delay in OnUpdate

Event called approximately after each TimerMilisec miliseconds. The actual delay may be larger than TimerMilisec miliseconds, depending on how the program (and OS) is busy.

You can of course change TimerMilisec (and OnTimer) even when some windows are already open.

Public property TimerMilisec: Cardinal read FTimerMilisec write FTimerMilisec default 1000; deprecated 'use TCastleTimer to perform periodic operations, or track time delay in OnUpdate';

Warning: this symbol is deprecated: use TCastleTimer to perform periodic operations, or track time delay in OnUpdate

 
Public property MainWindow: TCastleWindow read FMainWindow write SetMainWindow;

Main window used for various purposes. On targets when only one TCastleWindow instance makes sense (like Android or iOS or web), set this to the reference of that window. It is also used by TWindowProgressInterface to display progress bar.

Public property UserAgent: string read FUserAgent;

User agent string, when running inside a browser. Right now never set (was used by NPAPI plugin, may be useful to new web target).

Public property LimitFPS: Single read GetLimitFPS write SetLimitFPS; deprecated 'use ApplicationProperties.LimitFps';

Warning: this symbol is deprecated: use ApplicationProperties.LimitFps

 
Public property Version: string read GetVersion write SetVersion; deprecated 'use ApplicationProperties.Version';

Warning: this symbol is deprecated: use ApplicationProperties.Version

 
Public property TouchDevice: boolean read GetTouchDevice write SetTouchDevice; deprecated 'use ApplicationProperties.TouchDevice';

Warning: this symbol is deprecated: use ApplicationProperties.TouchDevice

 

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